Various types of extensible probe devices have been proposed which employ a flexible envelope which can be extended or retracted by means of positive or negative fluid pressure. These probes generally are in the form of relatively long inwardly foldable flexible film-like tubes with suitable rigid housings normally containing the folded tubes and with means to apply fluid pressure to the housings for causing the film-like tubes to be extended from the housings into a body cavity or tract through a body opening, such as the mouth, nose, anus or urethra. These prior art devices may be used to locate a tool, such as a catheter, within the cavity, but do not seek to use the extensible film-like tubes for the purpose of closely controlling and advancing an elongated tool or diagnostic examination device, nor for efficiently feeding such a tool or diagnostic device, into the body cavity under study.
While devices described in prior patents include means for everting a flexible tubing element from a rigid housing into a body passage and thereby inserting a relatively long section of everted tubing into the body passage under study, none of such devices provides for examination of the path ahead of the tubing as it is being advanced along the passageway. Where an interior element such as a tool, e.g. a fiber optic scope, is inserted along with the tube, in the prior art devices, the distance the tool is to travel before it is available for use must be predetermined because the tool moves 2x the rate of the everting tube, and therefore such element must be placed far back within the everting tube at the start, and cannot be used except when the whole assembly is extended the predetermined length.